Measurement and Analysis of Reactivity Worth of²⁴¹Am Sample in Water-Moderated Low-Enriched UO₂Fuel Lattices at TCA

Abstract

The reactivity worths of 22.82 grams of 241 Am oxide sample were measured and theoretically analyzed in water-moderated UO 2 fuel lattices in seven cores of the Tank-Type Critical Assembly (TCA) at the Japan Atomic Energy Agency for an integral test of 241 Am nuclear data. These cores provided a systematic variation in the neutron spectrum between the thermal and resonance energy regions. The sample reactivity worth was measured with an uncertainty of 2.1% or less. The theoretical analysis was performed using the JENDL-3.3 nuclear data by a Monte Carlo calculation method. Ratios of calculation to experiment (C/Es) of the reactivity worth were between 0.91 and 0.97, and showed no apparent dependence on the neutron spectrum. In addition, sensitivity analysis based on the deterministic calculation method was carried out to obtain the impact of changing the 241 Am capture cross section on the sample reactivity worth. The result of this analysis showed that the C/E could be significantly improved by almost uniformly increasing the 241 Am capture cross section of JENDL-3.3 by 25-30%.